1. Technical Field
The present disclosure relates generally to microwave surgical devices having a microwave antenna which may be inserted directly into tissue for diagnosis and treatment of diseases. More particularly, the present disclosure is directed to a microwave antenna having a cooled coaxial feed, radiating section and balun choke dielectric and a method of manufacturing the same.
2. Background of Related Art
In the treatment of diseases such as cancer, certain types of cancer cells have been found to denature at elevated temperatures (which are slightly lower than temperatures normally injurious to healthy cells.) These types of treatments, known generally as hyperthermia therapy, typically utilize electromagnetic radiation to heat diseased cells to temperatures above 41° C., while maintaining adjacent healthy cells at lower temperatures where irreversible cell destruction will not occur. Other procedures utilizing electromagnetic radiation to heat tissue also include ablation and coagulation of the tissue. Such microwave ablation procedures, e.g., such as those performed for menorrhagia, are typically done to ablate and coagulate the targeted tissue to denature or kill the tissue. Many procedures and types of devices utilizing electromagnetic radiation therapy are known in the art. Such microwave therapy is typically used in the treatment of tissue and organs such as the prostate, heart, liver, lung, kidney, and breast.
One non-invasive procedure generally involves the treatment of tissue (e.g., a tumor) underlying the skin via the use of microwave energy. The microwave energy is able to non-invasively penetrate the skin to reach the underlying tissue. However, this non-invasive procedure may result in the unwanted heating of healthy tissue. Thus, the non-invasive use of microwave energy requires a great deal of control.
Presently, there are several types of microwave probes in use, e.g., monopole, dipole, and helical. One type is a monopole antenna probe, which consists of a single, elongated microwave conductor exposed at the end of the probe. The probe is typically surrounded by a dielectric sleeve. The second type of microwave probe commonly used is a dipole antenna, which consists of a coaxial construction having an inner conductor and an outer conductor with a dielectric junction separating a portion of the inner conductor. The inner conductor may be coupled to a portion corresponding to a first dipole radiating portion, and a portion of the outer conductor may be coupled to a second dipole radiating portion. The dipole radiating portions may be configured such that one radiating portion is located proximally of the dielectric junction, and the other portion is located distally of the dielectric junction. In the monopole and dipole antenna probe, microwave energy generally radiates perpendicularly from the axis of the conductor.
A typical microwave ablation probe includes a transmission line that provides a microwave energy signal to the microwave antenna. The transmission line is enclosed in an elongated shaft and includes a long, thin inner conductor that extends along the axis of the probe and is surrounded by a dielectric material and is further surrounded by an outer conductor around the dielectric material such that the outer conductor also extends along the axis of the probe.
A cooling system may also be enclosed in the elongated shaft of the microwave ablation probe. For example, cooling fluid may be supplied to the distal end of the microwave ablation probe through one or more cooling supply lumens. After being deposited at the distal end of the elongated shaft the cooling fluid flows proximally through the elongated shaft through a return lumen, typically a chamber between the outer surface of the transmission line and the inner surface of the elongated shaft. In addition to providing cooling for the elongated shaft portion of the microwave ablation probe, the cooling fluid—also at least partially insulates the transmission line from the outer surface of the elongated shaft.
The coaxial construction of the monopole antenna, the dipole microwave antennas and the transmission line that provides a microwave signal thereto, include a dielectric sleeve that provides a dielectric junction between the inner and outer conductors.
Development of structurally stronger invasive probes have resulted in long, narrow, needle-like antenna probes which may be inserted directly into the body tissue to directly access a site of a tumor or other malignancy. Such rigid probes generally have small diameters that aid not only in ease of use but also reduce the resulting trauma to the patient.
Further improvements (i.e., a reduction in diameter, improved temperature management along the shaft and choke, and/or an improvement in strength) may be accomplished by combining the cooling system and the dielectric portions of the transmission line and/or the antenna, as disclosed in the present application.